ABSTRACT: Neoplasms of the mammary glands are common in carnivores but are very uncommon in herbivores. In this report, clinical, pathological, and immunophenotypical findings of pure? invasive micropapillary carcinoma in a mare are described. The mare was prostrated in poor nutritional condition, and a tumor in the mammary gland was detected at physical examination. Because of unfavorable prognosis, the mare was euthanized and necropsied. Grossly, there was a neoplastic growth in the mammary gland with metastasis to the regional lymph nodes. At histopathology, “in situ” infiltrative nests of cells in a micropapillary pattern were observed in the mammary gland and in the regional lymph nodes. Immunohistochemistry analysis revealed cytokeratin AE1AE3 and epithelial membrane antigen (EMA) positivity. Progesterone receptor labeled 25% of the neoplastic cells, estrogen receptor labeled 10% of cells, and there was negativity for HER-2 with incomplete and moderate membrane labeling (+). Nuclear labeling for Ki-67 was found in 8.7% of the neoplastic cells. This is the first report of pure invasive micropapillary carcinoma of the mammary gland in a mare.
The Veterinary quarterly 01/2011; 31(4-4):207-210. · 1.47 Impact Factor